5.) Open the Phoscon App (go to http://phoscon.de/app). You can now click on the gateway on the login page. The communication between browser and gateway takes place exclusively in the local network. If the gateway is not displayed, a search is started automatically. Afterward, you can repeat this anytime by clicking on the P logo.

6.) Follow the instructions in the app. First define a gateway name and a password.

7.) Then search for the devices (you need to perform a factory reset if they where already paired with an Philips HUE or similar)

8.) After the search finished press next

9.) You will then be prompted to create a room (if you do not already have one)

9.) The device is now connected to Phoscon/deCONZ.

Note: If you use thightvnc and login into your RaspberryPi you can see it connected inside deCONZ and can for example perform an firmware update as explained here.